How to turn all images in Kobo Forma to grayscale (to save space & speed xp)

[davidfor]

Originally Posted by droopy

Is there a way to do this for the ebook on the Forma, but keep the images in the library (i.e., the original copy of the book) untouched?

Just make a backup of the book and try it. Then, you can decide if it is worthwhile doing for other books.

Here is my prediction:

- It isn't going to reduce the space used enough to be worthwhile.
- When reading it on the ereader, you will keep picking up the tablet and looking at the pictures in colour. While doing that, you read the next bit and look at the pictures. You won't go back to the ereader to read any more of the book.

[droopy]

I made a backup of this big book.

The original book, as measured inside Calibre's library view, is 443.7MB.
After I opened the book editor and chose Tools>Compress_Images_Losslessly (I kept "Enable lossy compression of JPEG images" unticked/unchecked), the book became 417.9 MB.
That's a difference of 25.8 MB, or a savings of 5.8%.

[JSWolf]

Originally Posted by droopy

I have an ebook called Leonardo Da Vinci by Walter Isaacson. It's 450 MB because of the images. 450 mb is already 1/16 of my 8GB Forma space. Why transfer full-color images:
if I can't even enjoy the color,
if I can save storage space,
If I can speed page-loads/turns?

What I do is losslessly compress images at the Calibre default of 80. It makes them smaller. That might do well enough. Try it and see.

Given that you are worried about space, why didn't you get the 32GB Forma?

[JSWolf]

Originally Posted by droopy

In Calibre, I right-clicked the 500MB ebook and chose "Edit Book". In the left section of the book editor, I scrolled to the Images section and chose a 3.8MB jpg. Yup, it's high-res all right: 1390 x 2000 px. This ebook has a lot of these high-res, several-megabyte JPEG files.

Here's what to do. In the Calibre editor, reduce the size of the image to 1600 lines. Then after you've done that for every image that's larger then 1600 lines, losslessly compress at 80 all the images. You'll reduce the file sizes and you won't notice any difference. I don't notice on my H2O. That's about the best you'll be able to do realistically.

[droopy]

Originally Posted by JSWolf

What I do is losslessly compress images at the Calibre default of 80. It makes them smaller. That might do well enough. Try it and see.



Given that you are worried about space, why didn't you get the 32GB Forma?

Sorry, I just saw this message now. It seems that if I open use tapatalk app, I no longer get email notifications.

I'll try the lossless compression.

I thought that 8gb was enough. Had I known that some eBooks would be half a gigabyte, I'd have bought the 32gb Forma

[droopy]

Originally Posted by JSWolf

Here's what to do. In the Calibre editor, reduce the size of the image to 1600 lines. Then after you've done that for every image that's larger then 1600 lines, losslessly compress at 80 all the images. You'll reduce the file sizes and you won't notice any difference. I don't notice on my H2O. That's about the best you'll be able to do realistically.

Sorry for my delay in responding. I just saw your message now. I think when I use the Tapatalk app, email notifications no longer come into my inbox. I hope to try what you have so kindly suggested in the days ahead.